ANIMAL HEAT. 
tion of means to ends that is to be met with in 
any part of the animal economy. 
It was an opinion generally received among 
the older writers, and it was maintained even by 
Boerhaave, that life cannot exist in a tempera- 
ture higher than that which is natural to the 
body: but many facts have been lately brought 
to light which completely disprove this position. 
The first of them, which rested upon good author- 
ity, was communicated by Tillet and Duhamel. 
They gave an account of some young women, in 
the service of a baker, in one of the provincial 
towns in France, who were accustomed to enter 
the hot ovens for the purpose of turning the 
loaves; and this, it was said, was done without 
any apparent inconvenience, provided they were 
careful not to touch the heated surface. The 
narrative was scarcely credited at the time, but 
subsequent facts have fully established its credi- 
bility. A set of experiments were performed in 
London, by Blagden and Fordyce, in which a 
chamber was heated to a temperature higher 
than that of boiling water, and these gentlemen 
found that they could easily remain in it for an 
indefinite length of time. It is, however, to be 
regretted, that they almost exclusively directed 
their attention to the effects of the heated air 
upon the various substances in the room, and un- 
fortunately neglected to observe its action upon 
the living body itself. We are, indeed, informed 
that they perspired very copiously, but we have 
no information respecting the most important 
point, whether their temperature was actually 
raised ; or, at least, what we are told on this sub- 
ject is too vague to allow us to place much con- 
fidence in the statement. Some experiments 
have been lately performed by M. De la Roche 
which give us some insight into this intricate 
subject. He found that the body was capable of 
remaining in a temperature considerably higher 
than that which is natural to it, as long as there 
was a free access to the surrounding air; but 
that, when the animal was confined in a small 
space, an uneasy sensation was produced, and the 
temperature was elevated. Hence it may be con- 
jectured, that the evaporation of aqueous vapour 
from the lungs, and perhaps also from the surface 
of the body, is the means by which the super- 
abundant heat is carried off in these cases, so as 
to form a kind of balance to that operation, what- 
ever it be, by which heat is generated under 
ordinary circumstances. 
There is, however, much left for us to inquire 
into in this process. In the first place, we have 
to ascertain, to what degree a mass of matter, of 
the same capacity with the body, and of equal 
bulk, would have been heated at the same tem- 
perature with that to which the individuals were 
exposed in the above experiments. We know, 
that when air is much heated, it is proportion- 
ably rarefied; fewer particles of it, therefore, 
come into contact with the cold body, and hence 
the communication of heat will be much slower. 
ANIMAL MANURES. 
187 
Then, with respect to the animal functions taken 
in connexion with each other, we should examine 
what effect the respiration has, in these cases, 
upon the air taken into the lungs; is there any 
carbonic acid formed? and, if there be, what 
quantity is generated? We should be led by 
analogy to suppose, that the amount of oxygen 
consumed must be very small, so that the usual 
supply of heat would be cut off. Our next object 
should be, to discover whether the quantity of 
aqueous vapour discharged from the lungs would 
be sufficient to counteract the operation of all 
the sources, either internal or external, by which 
the body acquires heat, and we should then be 
able to decide upon a point which has been much 
agitated, whether there be any specific function 
for the purpose of cooling the body, or rather, 
whether the evaporation of the cutaneous and 
pulmonary vapour be alone sufficient for that 
purpose. There has been much vague specula- 
tion employed by physiologists, on the power of 
the body in generating cold. No part of the 
animal economy has been treated of in a more 
mysterious manner, and different metaphysical 
notions have been formed to account for an opera- 
tion, the existence of which has not yet been 
satisfactorily proved. What, however, we do 
know upon the subject, seems to warrant us in 
pointing out this part of the animal system, as 
an additional example of that beautiful adjust- 
ment of the functions to each other upon which 
we have already taken occasion to remark; for 
it appears, that not only have the lungs the 
power of evolving heat in greater or less quan- 
tity, in proportion to the demands of the system, 
but that the same organ, when necessary, can 
even produce the contrary effect, and generate 
cold. : 
ANIMAL MANURES. The excrements, flesh, 
bones, hair, wool, or putrescent products of ani- 
mals, employed as fertilizers of the soil. These 
substances act a highly conspicuous and most 
valuable part in the practical chemistry of agri- 
culture; and, as to at once their differences from 
one another, their several chemical constitutions, 
and their respective modes of action both separ- 
ately and in mixture, they ought to be thoroughly 
known by every farmer. Yet we cannot treat 
them at length as a separate topic, but must re- 
strict ourselves to some general remarks upon 
them, particularly upon animal excrements, and 
must refer, for a full view of them, to our arti- 
cles Manurss, Farm-YAarp Manure, Liguip Man- 
uRE, Nieut Sor, Urine, Guiin, Orn, Or-Caxs, 
Bones, Guano, Fisu, Gurne, Pouprerrs, AMMONIA, 
AzotE, and some others. 
The excrementitious matter of animals is 
partly solid and partly liquid, the former pass- 
ing through the intestinal canal, and the latter 
through the urinary passages ; and the solid kinds 
are habitually more or less dense, or more or less 
mixed with water, in the proportion in which 
the species of animal uses more or less of liquid 
